The Majority of Suicides Occur After Midnight

Posted on June 5, 2014 at 8:34 pm

New research reports significant evidence that suicides are much more likely to occur between midnight and 4:00 a.m., rather than during the day or evening hours.[1] In fact, researchers discovered that the mean suicide rate per hour was 10.27 percent after midnight, peaking at 16.27 percent between 2:00 a.m. and 2:59 a.m.1 In contrast, the mean suicide rate per hour for the time period between 6:00 a.m. and 11:59 p.m. was 2.13 percent.1 Therefore, the frequency of suicide between midnight and 5:59 a.m. was 3.6 times higher than expected.1

More than 38,000 Americans die from suicide each year, which far exceeds the 16,000 lives taken by homicide each year.1 Researchers believe that their new analysis may help to shed light on the causative or precipitating factors for suicide.1

“This appears to be the first data to suggest that circadian factors may contribute to suicidality and help explain why insomnia is also a risk factor for suicidal ideation and behavior,” said principal investigator Michael Perlis, PhD. “The results suggest that not only are nightmares and insomnia significant risk factors for suicidal ideation and behavior, but just being awake at night may in and of itself be a risk factor for suicide.”1

According to the researchers, previous research that suggested that more suicides during the day failed to account for the proportion of the population that is awake at each given hour.1 Therefore, their current study involved archival analyses of both the National Violent Death Reporting System, which provided data for the estimated time of fatal injury, and the American Time Use Survey, which provided an hourly proportion of the American population that is awake.1

Time of suicide was categorized into one-hour bins, and the hourly distribution of these data were weighted by the proportion of people awake at each hour and scaled to 100 percent.1 A total of 35,332 suicides were included in the analysis.1

According to Perlis, an important implication of the study is that treating insomnia may be a way to reduce suicide risk.1